In the field of medicine, it is often desirable to obtain small samples of body substances such as bone marrow for diagnostic purposes, and to withdraw somewhat larger portions of bone marrow for bone marrow transplant procedures. The latter may have particular importance in the treatment of certain blood disorders, such as leukemia.
The outer layer of marrow-containing bones is very hard, and considerable force must be employed to force a sharpened stylet or the like through this layer and into the marrow-containing cavity. The surgeon must exercise not only considerable strength, but also great care, to avoid slipping of the stylet on the bony surface and to properly position and orient the stylet so that the bone marrow cavity is reached.
On prior biopsy needle, shown in U.S. Pat. No. 3,628,524, included a hollow cannula and a stylet received in the cannula. The stylet terminated proximally in a head spaced proximally of the open end of the cannula, and was held to the cannula by means of a pin and slot arrangement. Small grips extended outwardly from either side of the cannula at its proximal end. In use, a surgeon would place a gauze sponge or the like in his palm, and the head of the stylet then would be pressed into the sponge, the surgeon grasping as he could the device with the index finger extending, for guidance, along the cannula.
In another device, the cannula itself was provided with a palm-contacting handle, the stylet terminating proximally in a palm-contacting surface substantially co-extensive with the handle so that distal force could be applied against both the cannula and the stylet. In this embodiment, the stylet and handle were locked together so that distal forces applied to the cannula alone were transmitted as well to the stylet.
Surgeons have found it difficult to grasp such bone marrow needles as are shown in U.S. Pat. No. 3,628,524 so that sufficient axial and rotative forces could be applied to drive the stylet through the hard, outer layer of a marrow-containing bone and yet precisely control the orientation of the stylet and the cannula of such needles. At times, it has been necessary to use a mallet to drive the sharpened stylet through the hard outer bone layer. With the device described above having a palm-contacting handle attached to the cannula, it is necessary to have a firm, yet releasable lock between the cannula and stylet so that movement of the cannula will result in coordinate movement of the stylet as well, such construction contributing to the cost of the needle.